Page 1
Prof. Roberto Verdone
www.robertoverdone.org
ZigBee
One among many:
a wireless enabling
technology for the IoT
world
28th May 2020
Francesca Conserva
[email protected]
Francesca Conserva
[email protected]
Outline
1. IoT ecosystem – A brief overview
2. Wireless Technologies – Which one?
3. Wireless Sensor Networks – Main
features
4. Requirements – Through the protocol
stack
5. To sum up – A very «practical» example
of WSN
Page 2
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
1. IoT ecosystem – A brief overview
Page 3
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
Smart Health Monitoring
EEG Sensor
ECG Sensor
Pressure Sensor
Temperature Sensor
Inertial Sensor
Blood saturation sensor
Blood pressure sensor
…
Page 4
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
Smart Cities
CO2 sensor
Fill-level sensor
Luminosity level sensor
Flow traffic sensor
…
Page 5
Prof. Roberto Verdone
www.robertoverdone.org
Smart Manufacturing
Environmental Monitoring
Smart Agricolture
Smart Farming/Animal Tracking
Smart Building
…
Francesca Conserva
[email protected]
Page 6
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
«How Smart, Connected Products Are Transforming Companies»
(Harward Business Review HBR, 2015)
«How Smart, Connected Products Are Transforming Competition»
(Harward Business Review HBR, 2014)
Market data and forecast future IoT trends
Sensors offer their
detection capabilities
to the Big Network
To modify, adapt, prevent, predict, whatever
kind of process within our ecosystem
Leading to: new services, new value for the
user, companies transformation,
(constructive) competition among verticals
Page 7
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
Market data and forecast future IoT trends
Spending on Internet of Things worldwide by vertical in
2015 and 2020
(Statista, March 2020)
Page 8
Prof. Roberto Verdone
www.robertoverdone.org
Use case
Francesca Conserva
[email protected]
Page 9
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
Two key aspects
Coordination
Wireless Sensor Network
Common set of rules
Wireless Technology
Wireless Sensor Network based on
IEEE 802.15.4/ZigBee
Page 10
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
2. Wireless Technologies – Which one?
Page 11
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
IEEE 802.15.4/ZigBee
Low/Medium Bandwith
Bc= 5 MHz Bit Rate = 250Kbit/sec
Short range
Outdoor < 100 m (LoS)
Drastical decrease indoor → Multi-Hoping is needed !
Standard solutions for wireless networks
High
BW
Medium
BW
Low
BW
Medium
RangeShort rangeVery short
rangeLong
range
Short range < 100 m
Very Short Range (typically) < few m
Page 12
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
Standard solutions for IoT
Heterogenous set of requirements
for IoT applications
Standardization of new
wireless solutions
Page 13
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
Standard solutions for IoT
Tipically Low Data Rate
& Short Range
Heterogenous set of requirements
for IoT applications
Standardization of new
wireless solutions
Page 14
Prof. Roberto Verdone
www.robertoverdone.org
Protocol stack architecture
Francesca Conserva
[email protected]
All the set of functionalities performed
by a node is organized in layers
Each layer performs tasks in agreement
with the corresponding layer at the
receiver side according to
communication protocol
The ensemble of all the communication
protocols defines a protocol stack
Page 15
Prof. Roberto Verdone
www.robertoverdone.org
Protocol stack architecture – IEEE 802.15.4/ZigBee
Francesca Conserva
[email protected]
IEEE 802.15.4
Defines the PHY and MAC
layers protocols
Standard de-facto for WSNs
Page 16
Prof. Roberto Verdone
www.robertoverdone.org
IEEE 802.15.4 – Main features
Francesca Conserva
[email protected]
Thought for low-cost, low-rate,
low-power consumption wireless
communications
Used for Low Rate W-PAN
composed of battery charged
devices
IEEE 802.15.4
Defines the PHY and MAC
layers protocols
Standard de-facto for WSNs
Page 17
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
3. Wireless Sensor Networks – Main features
Page 18
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
Wireless Sensors Networks – State of Art
Years
# S
cie
nti
fic
Pu
bli
ca
tio
ns
Page 19
Prof. Roberto Verdone
www.robertoverdone.org
Sensor
nodes
Gateway
Users
Monitored AreaHow does a WSN look like
Francesca Conserva
[email protected]
Other Nets
(e.g. Internet)
Page 20
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
Wireless Sensor Networks – Definition
A Wireless Sensor Network (WSN) in its simplest form can be defined as a
network of (possibly low-size and low-complex) devices denoted as nodes
that can sense the environment and communicate the information
gathered from the monitored field through wireless links
to a gateway, connected to other networks (e.g. Internet)
I.F. Akyildiz, Su Weilian, Y. Sankarasubramaniam, E. Cayirci, "A survey on sensor
networks,". Communications Magazine, IEEE, vol.40, no.8, pp.102,114, Aug 2002
Page 21
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
WSNs – 5 key aspects
Coverage
Connectivity
Energy Efficiency
Self-Organization
Scalability
Page 22
Prof. Roberto Verdone
www.robertoverdone.org
Gateway
Users
Monitored Area
Coverage
Francesca Conserva
[email protected]
The knowledge of the sensing range
together with the dimension of the area
to be monitored provides the node
density
It is an important aspect as some zones
might be not covered (coverage issues)
Page 23
Prof. Roberto Verdone
www.robertoverdone.org
The receiver sensitivity
is the lowest power level
at which the receiver can
detect an RF signal and
demodulate it
Connectivity
Power Loss through the Radio Channel
Francesca Conserva
[email protected]
Reference values of a freescale device
Page 24
Prof. Roberto Verdone
www.robertoverdone.org
Connectivity
Francesca Conserva
[email protected]
Reference values of a freescale device
Power Loss [dB] = Tx Power [dBm] – Receiver Sensitivity [dBm]
Max. Loss [dB] = Max. Tx Power [dBm] – Receiver Sensitivity [dBm]
freescale → Max. Loss [dB] = 4 [dBm] - (-96) [dBm] = 100 [dB]
Page 25
Prof. Roberto Verdone
www.robertoverdone.org
Transmission Range
From the PL [dB] →
Max. Transmission Range
Distance [m]
PL [dB]
The maximum transmission
range is the maximum
distance at which two nodes
can communicate
freescale →
Max. Loss [dB] = 4 [dBm] - (-96) [dBm] = 100 [dB]
Max Transmission range ≈ 100 m (Outdoor!)
Francesca Conserva
[email protected]
The curve holds in LoS
Conditions (Outdoor)
The transmission range
plays a crucial role in
the design of a WSN
Page 26
Prof. Roberto Verdone
www.robertoverdone.org
Gateway
Users
Monitored Area
WSN – Single Sink
Francesca Conserva
[email protected]
Sensor nodes
Sink (also referred to as Coordinator)
Page 27
Prof. Roberto Verdone
www.robertoverdone.org
Isolated node
Gateway
Users
Fully Connectivity
Connectivity and transmission
range are strictly related
If the transmission range of all the nodes is
such that they can communicate with the
sink, then the WSN is said to be fully
connected
If a WSN is not fully
connected, we have
to add more nodes
or sinks !
Francesca Conserva
[email protected]
Page 28
Prof. Roberto Verdone
www.robertoverdone.org
Gateway
Users
Monitored Area
WSN – Multiple sinks
Francesca Conserva
[email protected]
In some situations more than a single sink
might be needed
E.g. Smart Building - For each floor we
could have a sink that gathers data coming
from all the nodes. Then, each sink will
deliver these data to a gateway placed,
maybe, outside the building
The higher the number
of sinks, the more the
complexity of the
design
Page 29
Prof. Roberto Verdone
www.robertoverdone.org
Elements of a node
Francesca Conserva
[email protected]
• Sensor
• Transceiver
• Microcontroller
• Memory
All these parts are responsible
of energy consumption
Page 30
Prof. Roberto Verdone
www.robertoverdone.org
Gateway
Users
Monitored Area
WSNs with actuators
Francesca Conserva
[email protected]
Sensor nodes
Sink (also referred to as Coordinator)
Actuator nodes
Nodes can act as actuators
making the traffic different
Uplink: node-sink
Downlink: sink-node
Page 31
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
Energy Efficiency
Nodes generally cost few money, have low sizes as well as a low
energy consumption → Network lifetime is a typical
requirement in WSNs.
Understanding where and when a node consumes energy is
crucial in order to let the network live as much as possible.
Page 32
Prof. Roberto Verdone
www.robertoverdone.org
Where does the energy is spent?
Francesca Conserva
[email protected]
Power consumption
[mW]
The transceiver is the most energy consuming!
Generally nodes are
battery charged while
sink might need to be
plugged-in, as it
receives data from the
sensors of the entire
networks
Page 33
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
When does the energy is spent?
TR = D + S + T + I
Round duration
• Reception mode: the node receives the indication (query) to take measures by the sink
• Sensing: the node performs measures
• Transmitting mode: the node sends the data to the sink
• Idle state: the node can switch-off the TX/RX waiting for the next query
ER = Prec * D + Psens * S + Ptrasm *T + Pidle * I [Joule/round]
Energy spent / Round
Page 34
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
Energy Efficiency
All phases of the communication protocol must be designed to
minimise energy consumption
Nodes must turn off during inactive periods
Page 35
Prof. Roberto Verdone
www.robertoverdone.org
Gateway
Users
Monitored Area
Francesca Conserva
[email protected]
Self- Organization
Sensor nodes
Sink
Router
None central unit that manages
the network
Each node has to discover itself
whether to implement a
single/multi-hop communication
Every node should learn how to
reach the sink
1st hop
2nd hop
Page 36
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
Scalability
In many applications the number of nodes can be very large as well as the
kind of requirements to be satisfied (as we will see).
As a consequence, all protocols must be:
Able to work whatever the number of nodes
within the network
Very flexible and adaptive to the different user
requirements
Page 37
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
4. Requirements – Through the protocol stack
Page 38
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
Type of reporting
Estimation of spatial (and temporal)
random processes
Event Detection Req.s on delay
Req.s on
data losses
• Probability of false alarm
• Probability of missed detection
• Localization precision
• Latency
• Network lifetime
• *Sampling frequency has to ensure that the
process evolution is tracked
• Network lifetime
*Sampling frequence: in this context it refers to the periodicity with which a sensor takes samples (→ related to the Round duration)
Page 39
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
The wide range of requirements in terms of node densities,
sampling frequencies, latency, network lifetime (energy consumption),
etc, makes the design of WSNs extremely application-dependent.
In the design of a WSN, we have to start from the requirements that
come from the applications, thus the starting point is the application
layer.
Requirements – final considerations
Page 40
Prof. Roberto Verdone
www.robertoverdone.org
Layers’ tasks
Here, bits coming from the sensor are
passed to the μprocessor → data
aggragation, security issues
It finds the path to reach the final
destination → forwarding, routing
Reliable point-to-point communication →
error handling, access to the channel
(interference issues), …
Transceiver activation; modulation;
amplification; antenna connection
Francesca Conserva
[email protected]
Page 41
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
5. To sum up – A very «practical» example of WSN
Page 42
Prof. Roberto Verdone
www.robertoverdone.org
A WSN based on IEEE 802.15.4 for toilet paper detection
Green -Toilet Red -Toilet
Ba
thro
om
Francesca Conserva
[email protected]
Page 43
Prof. Roberto Verdone
www.robertoverdone.org
Green -Toilet Red -Toilet
Ba
thro
om
Francesca Conserva
[email protected]
Page 44
Prof. Roberto Verdone
www.robertoverdone.org
1° floor
Ground floor
How could we improve the project?
Francesca Conserva
[email protected]
Page 45
Prof. Roberto Verdone
www.robertoverdone.org
Multi-hoping!
Francesca Conserva
[email protected]
Page 46
Prof. Roberto Verdone
www.robertoverdone.org
Francesca Conserva
[email protected]
Thanks for your
attention